1. Field of the Invention
The present invention relates to a method for repairing a tubular conduit by applying a lining material on the inner wall of the tubular conduit.
2. Description of the Prior Art
When an underground tubular utility conduit or an underground industrial tubular conduit, such as a sewer pipe, a gas pipe and an electric conduit pipe, becomes defective or very old, the pipe is repaired and reinforced without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced in the field of civil engineering. Typically, the method is disclosed by Japanese Provisional Patent Publication (Kokai) No. 60-242038.
According to this publication, this method of pipe repair comprises inserting a sufficiently long tubular flexible liner bag into the pipe to be repaired by means of a pressurized fluid, like air or water. The tubular liner bag is made of a flexible resin-absorbent material impregnated with a thermosetting resin, and has the outer surface covered with a hermetic plastic film. More particularly, according to the publication, the tubular flexible liner bag is closed at one end and open at the other; the tubular flexible liner bag is first flattened, then, the closed end of the tubular liner bag is tied to a control rope; the open end of the tubular liner bag is made to gape wide and hooked at the end of the defective or old pipe in a manner such that the wide-opened end of the liner completely and fixedly covers and closes the pipe end; a portion of the liner is pushed into the pipe; then, the pressurized fluid is applied to the said portion of the tubular liner such that the fluid urges the tubular liner to enter the pipe. Since one end of the tubular liner is hooked at the end of the pipe, it remains there while the rest of the flexible liner bag is turned inside out as it proceeds deeper in the pipe. (Hereinafter, this manner of insertion shall be called "reversing".) When the entire length of the tubular liner bag is reversed (i.e., turned inside out) into the pipe, the control rope holds the closed end of the tubular liner bag to thereby control the length of the tubular liner in the pipe. Then, the reversed tubular liner is pressed against the inner wall of the pipe by the said pressurized fluid, and the tubular flexible liner is hardened as the thermosetting resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag by means of a hot steam, etc. It is thus possible to line the inside wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
However, in this repairing method, when the fluid employed to reverse and fill and press outward the tubular lining bag is a liquid such as water, it is necessary to heat the entire body of the liquid, and this consumes a considerable amount of fuel or electricity as well as time, especially if the diameter of the pipe is large or the length thereof is large. Also, since this method uses a large volume of the liquid, it requires a large-sized boiler, hot water pump, heating and circulation installation, etc., and the cost for such facility will be significant and the time and area required for setting up such large facility will be also increased.
For this reason, an improved pipe repair method was proposed by one of the present applicants which matured into U.S. Pat. No. 5,225,121. According to this method, as shown in FIG. 6, the tubular lining bag 102 impregnated with a thermosetting resin is inflated inside the tubular pipe 101 by means of pressurized air, and at the same time a hot water hose 106 having a plurality of holes is inserted into the tubular lining bag 102, and the hot liquid is ejected radially from the hot water hose 106 via the holes to heat the tubular lining bag 102 to thereby harden the thermosetting resin impregnated in the tubular lining bag 102.
In this hot water ejection method, the tubular lining bag 102 pressed onto the inner wall of the tubular pipe 101 is supposed to be uniformly heated by the hot liquid ejected from the hot water hose 106, so that the thermosetting resin impregnated in this bag 102 should be uniformly hardened, and since the amount of ejected hot liquid may be relatively small the amount of electricity or fuel required to heat the liquid for ejection can be considerably smaller than that required to heat the entire body of the liquid filling the tubular bag; consequently, the boiler, hot water pump, and other heating and circulation facilities may be of small size and compact. Also, even if the pipe to be repaired is large in diameter or length, the repair can be conducted in a relatively short time and at relatively low cost.
Incidentally, when the lining bag 102 is heated, the thermosetting resin in it undergoes an exothermic reaction and becomes very hot, but the temperature does not overly exceed the boiling point of the liquid, since the ejected liquid applied to the inner wall of the lining bag 102 absorbs the heat from the bag 102 as the liquid is heated and eventually evaporates. Thus, the hot liquid ejected to the lining bag 102 at first functions as the starter for the exothermic reaction of the thermosetting resin, and then functions as the temperature stabilizer.